1. Field of the Invention
The present invention relates to a photographing lens having data on colors of light before and after light passes through the photographing lens or a similar lens.
2. Description of the Related Art
In recent image recording technologies, an image can be recorded as a digital image signal. In a digital image recording system, it is important to reproduce the same color as the color perceived through the human eye on a display, a printing sheet, and the like, and the degree of significance of accurate color rendering in digital reproduction is increasing. There are various recording means for digital images. For example, an image picked up by an image pick-up device such as a CCD may be converted to an electrical image signal and recorded as a magnetic signal on a magnetic tape, or other medium, may be displayed on a display, may be printed on paper using a color printer, or may be copied. In any of these implementations, an optical image formed through a lens is converted to an analog or digital image signal, and is retrieved from the pick-up device and stored.
A photographing lens is not completely transparent or achromatic, and lens materials have an inherent color (inherent spectral transmittance) which varies in accordance with any applied coating (see FIG. 2). Consequently, the color perceived by the human eye through the photographing lens is different from the color directly perceived by the human eye (without looking through the photographing lens). Consequently, when the image formed by the photographing lens is converted and reproduced using an image signal, it is necessary to correct the image signal in order to obtain the same color as that directly perceived by the human eye without looking through the photographing lens (which will be referred to as the true color).
However, in the prior art in which an image of an object formed by the photographing lens is converted to image signals and recorded on a recording medium, no color data is available to show the change in color depending on the photographing lens. Consequently, in a known solution to correct the color, the digital image signal recorded on the recording medium is read therefrom and is indicated on a display, and the displayed image is directly compared with the object to be recorded or printed.
It is an object of the present invention to enhance the degree of coincidence of color between a manuscript and recorded image data, and to facilitate the correction of the color, by providing necessary data (to make colors before and after recording identical) to a photographing lens when the color image is recorded through an optical element such as the photographing lens.